Biology subjects

Heffern, M. C.

Publications and source records attributed to Heffern, M. C..

3 recordsLinked to original sources

bioRxiv2025

Metal ion binding of vimentin tail domain fragments

The intermediate filament (IF) protein vimentin is widely distributed in various cell types in the body and is vital for the proper maintenance of the cell cytoskeletal architecture, yet an extensive structural characterization of its head and tail domains remains elusive. Alterations in the assembly and organization of vimentin IFs, including filament network reorganization, have been associated with several diseases including cataracts, myopathies, and metastatic cancer. The C-terminal tail domain of vimentin is of increasing interest as it is essential for regulating the structure and mechanical properties of filament networks through interactions with divalent metal ions, but the molecular basis of these tail domain-metal interactions have not been characterized. In this work, we perform an in-depth analysis of the structural and metal binding properties of fragments of the vimentin tail domain. Mass spectrometry, and UV-Vis and circular dichroism (CD) spectroscopy reveal the direct binding of divalent copper (Cu(II)) to the last 11 residues of the tail domain. Solution nuclear magnetic resonance (NMR) and CD measurements show that in isolation, the complete vimentin tail domain is primarily disordered, and that Cu(II)-binding involves both the last 11 residues and another segment in the middle of the tail domain. Aside from these binding sites, Cu(II) does not induce any significant ordering of the tail domain. These findings further support the tail domain serving as a key metal binding region of vimentin and provide new insights into the important interplay between the tail domain and metals in vimentin IF physiology and pathology. O_FIG O_LINKSMALLFIG WIDTH=123 HEIGHT=200 SRC="FIGDIR/small/648257v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@fe39d0org.highwire.dtl.DTLVardef@85958eorg.highwire.dtl.DTLVardef@1dda6corg.highwire.dtl.DTLVardef@1ef0749_HPS_FORMAT_FIGEXP M_FIG C_FIG

biophysics↗

bioRxiv2025

High Glucose Diet Induces Hepatic Iron Overload Contributing to Metabolic Dysfunction

Iron is an essential biometal, critical in processes that include oxygen transport, mitochondrial respiration, and cell signaling. Iron dyshomeostasis is linked with hyperglycemia and associated metabolic disorders, but the underlying mechanisms are poorly understood. To investigate these mechanisms, we conducted a short-term, four-week, in vivo study on mice given water supplemented with glucose. The short time frame was sufficient to cause metabolic shifts in the liver towards triglyceride synthesis. We sought to comprehensively track iron trafficking by analyzing liver and serum markers of iron metabolism alongside LC-ICP-MS analysis of iron speciation, which is a new approach in this context. Glucose supplementation induced changes in iron regulation despite equal dietary iron intake between groups. Specifically, we observed increased uptake of transferrin-bound iron from the serum and an iron overload state in the liver. We developed and applied a cell-based models of this glucose-induced iron overload state and found that, on the one hand, the anti-diabetic drug metformin could restore iron regulation; on the other hand, the iron chelator, deferoxamine, could restore glucose metabolism. Taken together, our studies reveal that early hyperglycemia is sufficient to cause disruptions in iron regulations, pointing to iron overload as viable therapeutic target in metabolic dysfunction.

biochemistry↗

bioRxiv2024

Spatial Multiomics Lipids and Gene expression using MALDI In Situ Hybridization Mass Spectrometry Imaging

Current spatial gene expression methods use DNA microarrays, Next Generation Sequencing (NGS), and fluorescence microscopy to depict the pathological/histological architecture of tissues. While each of these techniques has its own advantages, they are often costly, time intensive, and limit sampling area. A newly developed mass spectrometry-based platform, MADLI ISH MSI, combines in-situ hybridization (ISH) with matrix-assisted laser desorption/ionization (MALDI) to indirectly detect mRNA through an azide-modified photocleavable peptide mass tag using a single RNA targeting probe sequence. To date, 20 photocleavable mRNA probes have been synthesized to provide cellular identity within full sagittal sections of fresh frozen murine brain. This information can then be combined with existing MALDI techniques to overlay metabolomic data, such as lipids, to connect the functional state of a cell with its expressed genes. Future directions include expanding upon the number of genes that can be targeted within a single experiment.

molecular biology↗